Based on the pool film boiling, the paper discusses the heat transfer coefficient of fogdrop jet into cutting zone to cool high temperature wall and then founds the model. It can be concluded by transient test in cryogenic pneumatic mist jet cooling high temperature titanium surface with different water flow, that when reaching the best cooling effect, the water flow of cryogenic pneumatic mist jet cooling as well as the materials vaporizing and involving phase change heat-transfer under certain temperature must be equivalent, and at that time, the heat transfer coefficient of cryogenic pneumatic mist jet cooling will reach the maximum.